Abstract:

As the west boundary fault of Songliao basin and the eastern margin of the Greater Hing’an Mountains, Nenjiang-Balihan fault belt is located in the central part of Northeastern China. Nenjiang-Balihan fault belt is considered traditionally to be a huge deep-seated fault with NNE-striking, and it is characterized by a normal fault or detachment fault. During  field work, the authors found a ductile shear zone in Lingxia area, the middle of the fault belt. By the measurement of structural elements, the micro-structure studies, the finite strain measurement, the studying of crystal preferred orientations of quartz determined by EBSD (electron back scatter diffraction) and the measurement of the dynamically recrystallized quartz grain size，the authors calculated the paleo-stresses for the deformation rocks in the ductile shear zone, it shows that the feature of Lingxia ductile shear zone is sinistral strike-slip, develops protomylonite-mylonite with ca. 400℃ deformation temperature, and quartz fabrics is mainly low temperature bottom surface fabrics with slip system of {0001}. Based on the previous achievements about the features and formation date, Neijiang-Balihan fault belt have experienced a sinistral strikeslip ductile shearing fault in middle Early Cretaceous (134-113 Ma), and the dynamic tectonic setting of the Nenjiang-Balihan are related to moving direction changing from NWW to NNW of the Western Pacific Izanagi plate obliquely subducting under the Eurasia plate.

Key words: Nenjiang-Balihan fault, Lingxia area, ductile shear zone, structural deformation, EBSD, sinistral strike-slip